It is recognized that add-on bidets should be designed with the following points in mind:
1. The connection of the water supply to an add-on bidet inevitably involves skilled installation work by a competent plumber, but nevertheless the rest of the work of installation of the bidet should be such as to require a minimum of skill and special tools. PA1 2. The designer should see to it that the manual water controls for the bidet are convenient to use, and progressive and controllable in their effect. PA1 3. The bidet should include a movable spray-arm that can adjust from a not-in-use position to an in-use position. In the not-in-use position, the arm should be unobtrusive, or even invisible. The spray-arm must not obtrude into the entry area of the toilet-bowl when the spray-arm is not in use. PA1 4. The water supply to the spray-arm should pass through the spray-arm pivot, so that there is no need for exposed hose-pipes. PA1 5. The bidet includes a seat which can be raised and lowered, and preferably the spray-arm is pivoted onto this seat, rather than for example, onto a housing that remains fixed to the toilet bowl. There is more room on the seat than on the fixed housing to stow the spray-arm when the spray-arm is not in use. Also, again to avoid the use of exposed hose-pipes, the water-supply should pass through the hinge-pivot on which the seat is mounted. PA1 (a) The seat can be moulded substantially as a constant-thickness item, which makes mass production of the seat a simple operation. PA1 (b) The seat is light, yet is strong and rigid. PA1 (c) The seat can be contoured with compound curvature when it is moulded. Such a moulded seat can be extremely rigid even though the material is quite thin, and the seat can be of pleasing yet functional shape and appearance. PA1 (d) The seat can be provided with bumpers, so that when the seat is down, there is a space between the channel shape of the seat and the rim of the toilet-bowl. This space can be used for the purpose of stowing or storing the spray-arm in its not-in-use position. The spray-arm is virtually completely hidden when not in use. However, the spray-arm can be quickly brought into its in-use position once the seat is raised. PA1 (i) The inner side-wall of the seat can act as a water splash-guard, especially if the inner side-wall extends all around the seat. Such a splash-guard prevents water passing through the gap between the seat and the toilet-bowl, so that the person using the bidet can be much more confident in that use if he or she knows that no splashing of the water can result. This feature is absent from the prior art. PA1 (ii) The moulded channel-shaped seat may be depressed at the front of the seat. This allows an access space for the hand of a person to be inserted. Preferably, the splash-guard continues all around the seat, including behind such a depressed region. PA1 (i) The fixed housing or mounting-means may be formed with relatively wide pivot-pin housings respectively at the ends of a relatively slim bridge-piece. This a very convenient shape from the point of view of providing a good stable location of the seat in an economical manner. Furthermore, the wide pivot-pin housings serve admirably to receive the knobs of the water control valves. PA1 (ii) If the seat is moulded with a channel-shaped cross-section, the sockets for receiving the pivot-pins can be conveniently provided simply by moulding the sockets into the other side wall of the channel. PA1 (a) The water flow can be easily controlled, yet the control is positive, quick-acting, and stable. PA1 (b) An ordinary spray-head produces jets that would impinge directly onto the body of the person using the bidet. Inevitably, the spray-head has to be some distance below the person's body, to allow room for his or her hands to contribute to the washing operation. Thus, if a simple spray-head were to be used, with its direct jets as described, the force of the jets would have to be quite strong. Many people find strong jets uncomfortable. They would prefer a high-volume flow at a low velocity, rather than a low-volume flow at a high velocity, which is what a conventional spray-head gives. PA1 (c) Another benefit over the conventional several-small-direct-jets type of spray-head is this. It is very common for jet-holes to become partially clogged with scale, but not all the holes become clogged at the same rate. Some holes remain almost at their original size; others become restricted. The effect is that in order to keep up a high-volume flow, the water has to be forced out of those holes that are still free at a higher pressure. The result is even more discomfort for the user. Furthermore, such high-pressure jets cause the water to be splashed. However, when the jets are made to coalesce back into a stream, as in the present invention, such an effect gives no problems. PA1 (d) The spray apparatus of the invention provides a large volume of water, which can easily be adjusted to the requirements of any person, man or woman, child or adult, vigorous person or invalid, without any of the discomfort or splashing associated with direct jets. Instead, the water is delivered in a soft, gentle, flow or stream. PA1 (i) As will be seen from a perusal of the description which follows, the spray-apparatus of the invention can be arranged so that the water emerges as an annular tube. This tube of water has a very coherent formation, and the water stream has very little tendency to break up, even when the volume of flow is turned down as low as a person might wish. Whether such a flow of water is large or small, a person can still characterize it as soft and gentle. The fact that the water emerges as a tube provides also another benefit. With a conventional spray-head, the height to which the water rises after emerging from the spray-head varies with the through-flow. When the stream is a tube, the height of the water still does vary with the through-flow, but not to the same degree as the variation that results from a conventional spray-head. With the tube, the water tends to fan out, in that the water emerges as a diverging cone at large through-flows. The water emerges as a converging cone at low through-flows. The height reached by the water is substantially the same, which clearly is a desirable feature in a bidet. The reason why the tube of water is able to converge may be the presence of the space inside the tube. The moving water creates a partial vacuum in that space, which sucks the water inwards. When the flow-rate increases, the momentum of the water starts to overcome the suction effect. PA1 (ii) Preferably, the bidet apparatus to which the spray is fitted has two such spray-heads. Preferably, each spray-head is individually adjustable as to the respective volumes of flow; from full-flow to substantially (but not quite) zero flow, each independently of the other. This controllability increases the convenience of the bidet to the user. PA1 (iii) Preferably, the water supply to the spray-heads is provided with manual controls arranged in this manner: first, both hot and cold water supplies are independently adjustable, by respective separate knobs, as to their relative volumes of flow for temperature control; second, the combined flow is adjustable by means of a further knob. The fact that the spray-heads are themselves also adjustable as to volume renders the whole system very controllable as to both flow quantity and temperature. A bidet often is used while the toilet cistern is being re-filled. When the cistern is full, there can be a sudden change in the relative pressure differential between the hot water supply and the cold water supply. It is important that the controls should be quick-acting and effective to minimize the user's discomfort if this happens, which they are if the controls are arranged as above. PA1 (iv) Preferably, the seat of the bidet is provided with a splash guard, so that the person who uses the bidet can have confidence that no splashing will result (even though splashing is less likely with the gentle flow of water, as described), no matter how vigorously the person washes.